1. Field of the Invention
This invention relates to a method of making coated quartz optical communications fibers and the coated fibers.
2. Background Information
Quartz optical communications fibers whose principal components are quartz in both the core and cladding and which contain extremely small amounts of refractive index regulators such as germanium, phosphorus, etc., offer the advantages of small diameter, heat resistance, weather resistance, flexibility, low loss, and high transmission capacity. As a result, they are widely used as communication media such as for public communications, long-distance communications, etc. In addition, the surfaces of quartz optical communications fibers are generally coated with a first coat in order to maintain the strength, for stress relaxation, and to prevent microbending by external forces. It is then coated with a final coat. The interior side of the first coat consists of a primary coat, for example, of urethane or phenylsilicone, which a large refractive index.
For the first coat, the prior art employs an addition-curable silicone composition in which a lower alkenyl group-containing organopolysiloxane is addition reacted with an organopolysiloxane possessing silicon-bonded hydrogen in the presence of a platinum-type catalyst. However, the use of such a curable silicone composition as a coating suffers from the drawback that said composition degrades the optical transmission properties of the above-mentioned fibers. As described in Electron Lett. 19, 1983 and Lecture Note No. 1126 from the 1984 General National Meeting of the Institute of Electronics and Communication Engineers of Japan (IECE Japan), this phenomenon is believed to be caused by a reaction between the hydrogen gas generated during curing of the addition-curable silicone composition and the germanium present in a quartz optical communications fibers in extremely small amounts as a refractive index regulator. Hydroxyl groups are thus formed which absorb light in the infrared region and the optical transmission properties are thus degraded.